Projected Beam Detector With Imaging Device

ABSTRACT

A method of installing a projected beam detector can include providing a radiant energy source, providing a reflector, and projecting a radiant energy beam from the source to the reflector. A multi-pixel sensor or camera can be provided. The beam can be reflected from the reflector back to the sensor. The distance between the reflector and the camera can be determined based on size of image of the reflector incident on the camera. Where incident intensity corresponds to expected intensity for a predetermined distance, the sensitivity can be set based on predetermined distance.

FIELD

The application pertains to projected beam smoke detectors. More particularly, the application pertains to such detectors which include image sensors to facilitate installation and maintenance of such detectors.

BACKGROUND

Existing projected beam smoke detectors can be difficult to install and align. Many times when the detector is installed, the technician believes that the installation has been done correctly and the system indicates no trouble conditions. But later, any slight movement of the product will cause a trouble condition. This is because the detector beam was not centered properly on the reflector.

At installation, or when subsequently providing maintenance to projected beam smoke detectors, it is often necessary for the installer to know the distance across the projected space in order to properly set the sensitivity. Currently, installers must independently measure the distance in some way or read it from drawings of the building. Once the distance is known, the proper sensitivity setting can be selected on the unit.

One known approach to addressing the above noted problem has been disclosed in U.S. Pat. No. 7,760,359 which issued Jul. 20, 2010 and is entitled, “Beam Detector Distance Measurement” which is assigned to the Assignee hereof. The '359 patent is hereby incorporated herein by reference. In the '359 patent the distance a beam travels between the detector's transmitter and receiver is measured. A sensitivity parameter of the detector could be set in response to the results of that measurement.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph of exemplary size of a received image of a reflector, in pixels, vs. distance for a predetermined reflector size;

FIG. 2 is a block diagram of a system in accordance herewith;

FIG. 3 is a flow chart illustrating aspects of a method in accordance herewith; and

FIG. 4 is a flow chart illustrating further aspects of a method in accordance herewith.

DETAILED DESCRIPTION

While disclosed embodiments can take many different forms, specific embodiments hereof are shown in the drawings and will be described herein in detail with the understanding that the present disclosure is to be considered as an exemplification of the principles hereof, as well as the best mode of practicing same, and is not intended to limit the claims hereof to the specific embodiment illustrated.

In embodiments hereof, projected beam detectors can automatically measure the distance across the projected space and set themselves accordingly. Such detectors can incorporate a multi-pixel image sensor, or camera. In accordance herewith, the beam alignment problem can be solved, in part, by comparing the received signal level during the installation and alignment to a known table of values.

In one aspect, a projected beam smoke detector can incorporate a CMOS camera. A reflector is provided, displaced from the detector. The distance across the projected space can be ascertained by determining the number of pixels that the reflector occupies in the field of view of the camera. The reflector has a known size and as the distance between the detector and the reflector decreases, the size of the reflector increases on the imaging device.

For example, as illustrated in FIG. 1, reasonable resolution in the distance measurement can be obtained in a detector with a CMOS camera having 0.5 Mpixel resolution and an 8 inch reflector. The resolution is limited by how much the distance must change in order to result in a one pixel change in the apparent size of the reflector. A change from 330 to 300 feet will change the size by one pixel. The resolution improves as the distance decreases.

FIG. 2 illustrates a diagram of a system 10 with a projected beam detector in accordance herewith. System 10 includes a plurality 12 of ambient condition detectors 12-1 . . . 12-n. The members of the plurality 12 are coupled by a medium 14, which could in part be wired and/or in part wireless all without limitation, to a regional monitoring control unit 18. Members of the plurality 12 could include smoke detectors, heat detectors, fire detectors, gas detectors all without limitation.

Regional monitoring system 12, 14 and 18 could be installed and configured, as those of skill will understand so as to monitor ambient conditions at a plurality of locations in a region R. For example, unit 18 could be configured so as to monitor the region R for fire, smoke or gas conditions all without limitation.

Exemplary detector 12-1 could be implemented as a projected beam smoke detector with a housing 20 that carries a programmable controller 22. Controller 22 could include hard wired circuitry 22 a, one or more programmable processor(s) 22 b and executable control software 22 c encoded on a computer readable medium such as semi-conductor, magnetic, or optical storage. The processor(s) 22 b could execute the software 22 c to carry out one or more methods as described subsequently.

Controller 22 is also coupled to emitter drive circuitry 24 a. Drive circuitry 24 a is in turn coupled to a source or emitter 24 b of a beam of radiant energy BE. For example, emitter 24 b could be implemented as a laser, laser diode, or LED so as to emit mono-chromatic light.

A reflector 26 is displaced from detector 12-1 and positioned so that the incident beam BE reflects therefrom, as beam BR, and returns to housing 20. The reflected beam BR is incident on CMOS camera or imaging sensor 28 a. Camera 28 a is coupled to interface detector circuitry 28 b. Circuitry 28 b couples one or more signals indicative of the image sensed by the camera 28 a to controller 22.

FIGS. 3, 4 illustrate aspects of methods 100, 200 which can be implemented by a detector such as detector 20 of FIG. 2. Reflector identification can be implemented in accordance with method 100, when an image of reflector 26 is detected on camera 28 a, as discussed above as a result of flashing emitter 24 b, that image can be captured, as at 102. That image might include one or more bright spots indicative of objects in the field of view (FOV) of camera 28 a.

Subsequently as at 104, reflector candidates in the FOV can be identified. The size (expressed in number of pixels on the camera 28 a) of the various candidates can be determined as at 106. The distance between the reflector 26 and image on the camera 28 a, for each of the candidates, can be determined, as at 108, via a graph as in FIG. 1, since the size of the reflector is known along with the number of pixels on the image of the camera 28 a for each candidate.

The average intensity of each of the candidates can be determined, as at 110. The intensity for each candidate in the field of view can be corrected to take into account the image's location in the FOV of the camera 28 a, as at 112 using a pre-stored table of expected brightness vs. distance. For example, when the LED or laser source illuminates the camera, the expected intensity may not be received due to the location of a candidate in the FOV.

The measured intensity can be compared to the expected value for a given distance between the reflector 26 and the camera 28 a, as at 114. If there is no mismatch, as at 116, the valid reflector(s) can be identified, as at 118. In the event of a mismatch, that candidate can be rejected, as at 120. Images from an identified reflector can be used subsequently in detecting the presence of smoke in a region being monitored.

Sensitivity can be checked, or set in connection with aligned detectors with centered reflectors in accordance with method 200 of FIG. 4. With respect to method 200, an image of a reflector can be captured, as at 202. The size of the reflector, in pixels, can be determined, as at 204.

The distance between the reflector and the camera 28 a can be determined, as at 206. Optionally, a display thereof can be provided as at 208.

The average intensity of the pixels of the reflector can be determined as at 210. The measured intensity can be compared to the expected value for the determined distance, as at 212. Where there is no mismatch, as at 214, the sensitivity of the detector can be set or verified as at 216.

Advantageously, as discussed above, the average intensity of pixels of the camera 28 a should fall within an expected range for a given distance. If they do not, an error or trouble indicator can be generated, or produced. Also, the size of the reflector 26 on the camera 28 a can be periodically checked. It should remain constant over time. In a test mode, the image from the reflector may be partially blocked. Accidental blockages can also be detected.

Different sensitivities can be established for multiple reflectors within a field of view at different distances. In this regard, a sensitivity can be established for a reflector in the foreground, and, a different sensitivity can be established for a reflector in the background.

Sensitivity can be set based on distance. This can be useful where there are requirements for predetermined sensitivities for predetermined distances.

Reflector images can be qualified using size vs. signal strength. A reflector image can be tracked over time to detect movement due to building settling, or other anomalies.

From the foregoing, it will be observed that numerous variations and modifications may be effected without departing from the spirit and scope of the invention. It is to be understood that no limitation with respect to the specific apparatus illustrated herein is intended or should be inferred. It is, of course, intended to cover by the appended claims all such modifications as fall within the scope of the claims.

Further, logic flows depicted in the figures do not require the particular order shown, or sequential order, to achieve desirable results. Other steps may be provided, or steps may be eliminated, from the described flows, and other components may be add to, or removed from the described embodiments. 

1. A projected beam detector comprising: a source of a beam of radiant energy; a reflector; and control circuits including a multi-pixel sensor of radiant energy wherein an image from the sensor provides an indication of distance between the reflector and the sensor.
 2. A detector as in claim 1 wherein the beam from the source is reflected to the sensor.
 3. A detector as in claim 1 wherein a selected distance between the reflector and the sensor is indicated by the extent that the image from the reflector covers the sensor.
 4. A detector as in claim 3 which includes a port for optically viewing an image incident on the sensor.
 5. A detector as in claim 3 which includes visual feedback to facilitate alignment of the beam and the reflector.
 6. A detector as in claim 3 wherein the control circuits process sensor signals to identify reflector candidates in the field of view of the sensor.
 7. A detector as in claim 6 wherein the control circuits determine a size parameter of each of the candidates.
 8. A detector as in claim 7 wherein the control circuits determine a distance parameter for each of the candidates.
 9. A detector as in claim 8 where the control circuits establish an intensity for the candidates and correct intensity for position in a field of view.
 10. A detector as in claim 9 where the control circuits compare adjusted intensities to an expected value for a predetermined detector distance.
 11. A detector as in claim 1 which includes at least a second reflector, and, wherein a second image incident on the sensor provides an indicator of distance between the second reflector and the sensor.
 12. A method comprising: providing a radiant energy source; providing a reflector; projecting a radiant energy beam from the source to the reflector; providing a multi-pixel sensor; reflecting the beam from the reflector to the sensor; and determining a distance parameter between the reflector and the sensor based on size of reflector image.
 13. A method as in claim 12 which includes moving one of the reflector or the sensor and thereby adjusting the image on the sensor.
 14. A method as in claim 12 which includes centering the image on the sensor and directing radiant energy at the reflector.
 15. A method as in claim 12 which includes detecting distance between a reflector and the sensor based on the number of pixels of reflector captured on the sensor.
 16. A method as in claim 15 which includes measuring average intensity of a reflected image.
 17. A method as in claim 15 which includes comparing measured intensity to expected intensity for a predetermined distance.
 18. A method as in claim 17 which includes setting sensitivity based on a predetermined distance.
 19. A method as in claim 12 which includes providing a display device having a rectangular, multi-pixel display surface, and displaying an image incident on the sensor.
 20. A method as in claim 12 which includes providing multiple reflectors at varying distances from the sensor thereby establishing multiple sensitivities. 